The direction of sunshine or the installation sites of environmental control facilities in the greenhouse result in different temperature and humidity levels in the various zones of the greenhouse, and thus, the production quality of crop is inconsistent. This study proposed a wireless-networked decentralized fuzzy control scheme to regulate the environmental parameters of various culture zones within a greenhouse. The proposed scheme can create different environmental conditions for cultivating different crops in various zones and achieve diversification or standardization of crop production. A star-type wireless sensor network is utilized to communicate with each sensing node, actuator node, and control node in various zones within the greenhouse. The fuzzy rule-based inference system is used to regulate the environmental parameters for temperature and humidity based on real-time data of plant growth response provided by a growth stage selector. The growth stage selector defines the control ranges of temperature and humidity of the various culture zones according to the leaf area of the plant, the number of leaves, and the cumulative amount of light. The experimental results show that the proposed scheme is stable and robust and provides basis for future greenhouse applications.

Abstract. Hydroponics can allow crops to grow faster and can reduce plant pathogens. However, hydroponic systems have several disadvantages, of which the two most important are: (1) improper management or dramatic changes in the electrical conductivity (EC) and pH of the nutrient solution can harm the plant roots and affect the plant growth, and (2) system operators need to monitor the nutrient solution and replenish it regularly, thereby increasing the labor cost. Therefore, this study developed a micro-electro-mechanical systems (MEMs) based mixing system for hydroponic nutrient solutions based on fuzzy rule-based inference, which uses a micro-controller as the core and controls the output of five nutrient solution tanks to the mixing tank. The proposed system maintained an appropriate range of pH and EC in the mixing tank. Operators can view the changes in pH, EC, dissolved oxygen (DO), and other values in the nutrient solution on a graphic user interface. Moreover, operators can manually or automatically mix the nutrient solution. The system has been implemented in a hydroponic cultivation system, and the analysis results are discussed in this article. Keywords: Fuzzy logic, Hydroponics, Microcomputer.